Has there ever been a more important comma than the one in this title – Horizon: Eat, Fast and Live Longer (BBC2)? Lynne Truss, if you're reading, miss that baby at your peril. You'll (Usain) bolt your official Maccy D's down believing this will lead to eternal youth. Suddenly you're dead. And obese to boot!

No, it means eat, then fast, as in don't eat. Because they (scientists and that) reckon there's a link between calorie restriction and longevity. Michael Mosley is off on a fascinating journey to find out – in the US, a country obviously famous for its calorie restriction. Actually, and fascinatingly, during the Great Depression of the 1930s, life expectancy increased, by six years.

So Michael meets a man who doesn't eat very much. They do some tests; this guy's basically immortal, whereas Michael, who doesn't look too bad to be honest, isn't. But who wants to live for ever if you're going to be hungry?

Not Michael. So he goes to see another man who knows all about the growth hormone IGF-1 and about fasting, and who seems to be doing very well out of it because he drives a lovely red vintage Ferrari, which Michael squeezes awkwardly into. And which Michael then uses to squeeze (also awkwardly) in a motoring analogy. When we eat a lot, our cells are locked in the grow mode, which makes them susceptible to cancer and diabetes: "It's basically like slamming your foot on the accelerator, saying 'go go go'," he says. Yes, agrees Mr IGF-1, hopping on/in the metaphor bandwagon/Ferrari. "It's like driving your car all the time and never taking it to the mechanic." (And I've caught it too, because I've taken a wrong turn and I'm all tangled up in analogy spaghetti junction myself.)

Anyway, it's time for Michael to take his foot off the pedal and go slow – which is to say fast, the verb. He does, for three days. It's not the easiest thing to make into captivating television, because he's essentially not doing something. Plus he's a bit grumpy. So they employ some reality TV tricks; the crew go out for a meal at a Korean restaurant, they bring Michael along, to watch. Ha! Nice one. If in doubt, play the cruelty card.

The results are impressive though, in terms of lower growth hormones and diabetes. In just a few days Michael has dramatically reduced the risk of a whole bunch of age-related diseases. But a three-day fast is a hell of a thing to go through, and he'd have to do it every month or two, to keep the lovely red vintage Ferrari in pristine showroom condition, so to speak.

There is another, easier, way: intermittent fasting, on alternate days. It's not total starvation either – one day you get to eat 500 to 600 calories (400 to 500 for women). And on the other day, the feast day, you get to eat what the hell you like. A proper American diet even: Maccy D's, Taco B, Krispy K, the lot. And it has most of the same benefits as the total three-day fast. Maybe you don't get to live forever, but you live a hell of a long time. And you never look a day over 30. ADF they call it, for alternative day fasting. No, I don't like that and anyway, ADF is already Asian Dub Foundation. I'm going to call it the Dorian Gray Diet. Get involved, as Michael does.

But I can't start now, because I've got something on tomorrow night. And then there's that thing at the weekend (OK, so there's nothing at the weekend, but maybe I'll get a late invite). Anyway, what's the hurry? And obviously I need to get a portrait comissioned and painted, The Picture of Sam Wollaston, to then be hidden away, in the loft.

Thank you to Dispatches for Britain's High Street Gamble (Channel 4), Michael Crick's excellent investigation into the blight that is betting shop Britain. There are some winners: PaddyPower, Ladbrokes, William Hill, Coral etc. Virtually everyone else is a loser, most of all the sad addicts pumping money they can't afford into fixed odds betting terminals, the reason for the proliferation of bookies.

To blame? Labour's Gambling Act. They might as well have said: yeah, so all the shops are closing in disadvantaged areas all over the country? Well, that's OK, we'll make it really easy for thousands of crack houses to open in their place. Advertise? Of course they can, it's a free country isn't it?

"It's a load of bollocks, believe me," says a local of Deptford whose high street is being taken over. Mister, I do.